Structure-activity, biochemical and antiviral studies on griffithsin (GRFT), cyanovirin(CV-N) and scytovirin(SVN) continue. Currently, we are continuing the clinical development of GRFT as an anti-HIV microbicide. The first Phase I clinical trial has now been successfully completed with a second ( from another collaboration) currently accruing patients. We have also recently begun collaborating with the Centers for Disease Control on the use of these antiviral proteins against both Nipah virus and Rabies. To potentially use PCMBS lectins as anti-HIV microbicides, whose largest need is in resource-poor countries, it was necessary to find large-scale, low-cost methods of production. To address this requirement, we collaborated broadly with researchers to develop options for the agricultural production of these proteins. We have now completed large scale production of the proteins GRFT and CV-N in plants including tobacco, rice and soy. The PCMBS has steadily collaborated with the MCL to enable structure determination of the bioactive proteins we discover. We have worked with Dr. Alex Wlodawer's group to define the structure of CV-N, SVN and GRFT. During the current review period we have continued this collaboration to evaluate modified GRFT mutants and characterized several GRFT-tandemers with improved potency. GRFT is now entering first-in-human clinical trials as an anti-HIV microbicide with one Phase I clinical trial underway and a second slated to start in 2019. The PCMBS continues to isolate and characterize new anti-HIV proteins from aqueous natural product extracts. We have been working on a new protein isolated from the sponge Vagocia sp, from which no bioactive compounds have so far been reported. Initial studies on the protein fraction of this extract identified potent anti-HIV activity that appeared to bind to HIV-1 gp120. A protein, named vagocin, has been purified to homogeneity by a combination of precipitation techniques, hydrophobic interaction and anion exchange chromatography. Vagocin was shown to have an anti-HIV-1 EC50 of 4.4 nM in whole-cell anti-HIV assays. Additional anti-HIV screening of vagocin using the TzmBl assay system, performed with our collaborator ImQuest Biosciences, showed that the protein had activity against several clades of HIV-1 in the mid- to low-nanomolar range, with clade C being the most sensitive. Vagocin also inhibited cell-to-cell transmission of HIV and was found to be synergistic with the anti-HIV monoclonal antibody b12 and to a lesser extent with GRFT. We have produced rabbit polyclonal antibodies to vagocin which we will use to further define its binding interactions. We have also recently isolated and characterized a novel cyclic protein that allosterically inhibits the TDP1 enzyme. In addition, we have recently isolated a new anti-HIV protein from the soft coral Alertigorgia sp. This protein has low nano molar activity against HIV and is 10 kDa in size.